Motor vehicles, airplanes, helicopters, and ships are increasingly equipped with various sensors or camera systems. Examples are camera systems, such as video cameras, night vision cameras, residual light amplifiers, laser range finders, or passive infrared detectors. Motor vehicle identification systems are also increasingly used, for example, for toll collection.
Camera systems can use light in the ultraviolet (UV), visible (VIS), and infrared wavelength range (IR). Thus, objects, motor vehicles, and people can be precisely detected even during poor weather conditions such as darkness and fog. In motor vehicles, these camera systems can be placed behind the windshield in the passenger compartment. Thus, even in road traffic, they offer the capability of detecting hazardous situations and obstacles in a timely manner.
However, because of their sensitivity to weather conditions or airflows around the vehicle, such sensors must, in all cases, be protected by panes transparent to radiation. The sensor can be installed inside a motor vehicle. To ensure optimal function of the optical sensors, clean and condensation-free panes are absolutely essential. Condensation and icing clearly interfere with functionality since they clearly reduce the transmission of electromagnetic radiation. Whereas wiper systems can be used for water drops and dirt particles, they are usually inadequate in the case of icing. Here, systems that heat the pane segment associated with the sensor as needed at least briefly and thus enable uninterrupted use are essential.
Increasingly, panes have whole-surface coatings that are electrically conductive and transparent to visible light that protect, for example, the interior against overheating due to sunlight or overcooling or that effect selected warming of the pane upon application of an electric voltage. The panes with electrically conductive transparent coatings are, however, not suitable as transparent protective panes for sensors or camera systems because data-bearing radiation is not adequately transmitted through the coating. Consequently, the panes are customarily decoated in locally delimited regions and form a communication window for sensors and camera systems.
EP 1 605 729 A2 discloses an electrically heatable pane with a communication window. This communication window is kept free of condensation and ice by a heating device. The heating element is laminated into the pane at the position of the communication window. In addition, yet another heating element can be applied on the surface of the pane. The additional heating element is preferably printed onto the surface of the pane as conductive paste.
However, for this, it is necessary, in order to supply the heating conductor with electrical energy, to establish electrical contact with a power supply via current carrying strips.